Generally, an air-conditioner for vehicles is an apparatus that draws air from inside and outside a vehicle, cools or heats the drawn air using a heat exchanger, and blows the air, which has undergone the heat exchange process, into the vehicle.
Such an air-conditioner includes an air-conditioner casing, a blower, and an intake. An evaporator and a heater core are provided in the air-conditioner casing, and vents are provided on the outlet side of the air-conditioner casing. The opening ratio of each vent is controlled by a corresponding door. The blower is provided on the inlet side of the air-conditioner casing. The intake is installed to cover the blower.
A driver manipulates a control unit which is provided in a vehicle, so that the air-conditioner of the vehicle may be set to a cooling or heating mode, a vent mode, a bi-level mode, a floor mode, a mix mode, or a defrost mode.
The doors provided on the respective vents are manipulated by a driver, thus opening a specific vent for discharging the air into the vehicle. Further, a temp door is controlled, or the quantity of coolant fed into the heater core is controlled. Thereby, the temperature in the vehicle is regulated.
FIG. 1 is a perspective view showing a conventional intake of an air-conditioner of a vehicle. The conventional intake includes a housing 3 and a main door 4a. An outdoor-air inlet port 1, which communicates with the exterior of the vehicle, and an indoor-air inlet port 2, which communicates with the interior of the vehicle, are provided in the housing 3. The main door 4a rotates about a main-door drive shaft 5 while tracing an arc, thus opening or closing the outdoor-air inlet port 1 or the indoor-air inlet port 2 (see FIG. 2).
FIG. 2 is a schematic view illustrating the operation of the intake of FIG. 1. FIG. 2a shows the state in which the main door 4a closes the outdoor-air inlet port 1 but opens the indoor-air inlet port 2, so that indoor air flows through the indoor-air inlet port 2. FIG. 2b shows the state in which the main door 4a opens the outdoor-air inlet port 1 but closes the indoor-air inlet port 2, so that only outdoor air flows into the intake through the outdoor-air inlet port 1.
That is, the intake of the air-conditioner constructed as described above draws only outdoor air when an outdoor-air mode is selected by a driver. Conversely, when an indoor-air mode is selected, only indoor air is drawn into the intake.
However, such an air-conditioner is problematic in that, if the outdoor-air mode is selected in winter, only outdoor air is fed into a vehicle through the outdoor-air inlet port 1 during the operation of the air-conditioner, so that the performance of the air-conditioner is deteriorated. Further, when only indoor air circulates through the indoor-air inlet port, the interior of the vehicle becomes foul, thus harming a passenger's health.
In order to solve the problem, an intake, which draws a small quantity of indoor air even in the outdoor-air mode in order to enhance heating efficiency, has been proposed. This intake is shown in FIG. 3.
As shown in FIG. 3, the intake is provided with a flat-plate-type main door 4b between an outdoor-air inlet port 1 and an indoor-air inlet port 2. The main door 4b is connected to an actuator (not shown) via a drive shaft 5. Thus, as the main door 4b rotates about the drive shaft 5, the outdoor-air inlet port 1 or the indoor-air inlet port 2 is opened or closed. A subsidiary indoor-air inlet port 7 is formed in the upper portion of the main door 4b. A subsidiary door 6 is provided on the subsidiary indoor-air inlet port 7, and is rotated to open or close the subsidiary indoor-air inlet port 7.
When the main door 4b opens the indoor-air inlet port 2 and closes the outdoor-air inlet port 1, the subsidiary indoor-air inlet port 7 is closed by the subsidiary door 6 due to its own weight. Thus, in the indoor-air mode, outdoor air is not drawn into the intake, instead, only indoor air is drawn into the intake.
Meanwhile, in the outdoor-air mode, the main door 4b opens the outdoor-air inlet port 1, and closes the indoor-air inlet port 2. Thereby, outdoor air is drawn into the intake through the outdoor-air inlet port 1, and the subsidiary indoor-air inlet port 7 is partially opened, so that some indoor air flows into the intake. The subsidiary door 6 opens the subsidiary indoor-air inlet port 7 using the difference in pressure occurring when a blower fan 12 is operated and the weight of the subsidiary door 6. Thus, in the outdoor-air mode, some indoor air is also fed through the subsidiary indoor-air inlet port 7, in addition to outdoor air.
Therefore, the above-mentioned intake is advantageous in that, when the air-conditioner is set to the outdoor-air mode and a heater is operated to heat the interior of a vehicle, in the case where the outdoor temperature is much lower than the indoor temperature, as in winter, outdoor air is fed through the outdoor-air inlet port 1, and some of the indoor air is fed through the subsidiary indoor-air inlet port 7, so that the outdoor air is mixed with the indoor air, and heating efficiency is thus increased. However, such an intake is problematic in that the main door 4b has the shape of a flat plate, so that it cannot be applied to the intake shown in FIGS. 1 and 2. Further, since the subsidiary door 6 is rotatably connected to the main door 4b and is opened or closed using its own weight or a difference in pressure, the subsidiary door may malfunction because of abrasion or corrosion at the junction of the subsidiary door 6 and the main door. Furthermore, since the opening of the subsidiary door 6 is not controlled at a constant ratio, the quantity of indoor air drawn through the subsidiary indoor-air inlet port 7 is irregular. Thus, it is impossible to precisely control the quantity of indoor air that is drawn into the intake.